Writing board or slate and method of making same



Patented cc. 23, 1924:.

UNEEE ST GUSTAV WETTEB, OF WEESEN, SWITZERLAND.

WRITING BOARD OR SLATE AND METHOD OF MAKING SAME.

No Drawing.

Application filed August 29, 1921. Serial No. 496,656.

(GRANTED UNDER THE PROVISIONS 03? THE ACT OF MARCH 3, 1921, 41 STAT. In,1313.)

To all whom it may concern:

Be it known that I, GUSTAV Wnrrnn, a citizen of the Republic ofSwitzerland, residing at VVeesen, Switzerland, have invented certain newand useful Improvements in lVriting Boards or Slates and Methods ofMaking Same (for which I have filed applications in Switzerland August26, 1920, and in Germany on September 7th, 1920), of which the followingis a specification.

This invention relates to improvements in a method for making writingboards and slates. It has already been proposed in preparing the Writingsurface of slates and the like, on which the writing must be easilyobliterated, to utilize water-glass and earthy colors with certainadditions for instance of silicate of magnesia or of silicic acid andpulverulent carbonate of lime, which mixture is applied as a coveringlayer to a base part. Writing surfaces of this kind have not provedsuccessful as it has been found extremely difficult to apply a uniformcovering layer of such materials and further this layer becomes hard,cracked and blistery.

The object of the present invention is to overcome the above mentioneddisadvantages and to provide for a durable writing surface that respondsto all the requirements. According to the invention the covering layerapplied to a base part consists of water-glass and zinc-white to whichlayer a further covering layer of a solution of Water-glass is applied.To the first layer consisting of water-glass and zincwhite a smalladdition of a colouring matter may be made in order to produce a writingsurface of a desired colour.

As base cardboard, paper, wood, asbestos cement, slate, steel plate orother materials may be used. Writing on the surface prepared accordingto the invention can be effected with pencil, coloured crayon or thelike as well as with water colours or an ink that is free of acids. Thewriting or drawing may easily and completely be obliterated by means ofa sponge or the like.

The slate itself may be of any shape. It may also be provided with aframe.

I claim:

1. A process for preparing writing surfaces on slates, boards and thelike, consisting in applying a cover layer of waterglass and zinc-whiteto a surface of a base, and in applying a layer of a water-glasssolution to said covering layer.

2. A process for preparing writing surfaces on slates, boards and thelike, consisting in applying a covering layer of waterglass andzinc-white with an addition of a colouring matter to a surface of abase, and in applying a layer of a water-glass solution to said coveringlayer.

3. A slate or board for writing purposes, comprising a base adapted toform at least one writing surface, a covering layer consisting ofWater-glass and zinc-white applied to said writing surface, and a layerconsisting solely of water-glass applied to said covering layer.

4. A slate or board for Writing purposes, comprising a base adapted toform at least one writing surface, a covering layer consisting ofwater-glass and zinc-white with an addition of colouring matter appliedto said writing surface, and a layer consisting solely of water-glassapplied to said cover ing layer.

In testimony whereof I affix my signature.

GUST WETTER.

